Spacer for transformer coils



J. G. FORD SPACER FOR TRANSFORMER COILS Filed May 6, 19158 May 14, 1940.

I INVENTOR Patented May 14, 1940 UNITED STATES PATENT OFFICE SPACER FOR TRAN SFOBMER COILS Pennsylvania Application May 6, 1938, Serial No. 206,358

1 Claim. (Cl. 175-362) This invention relates to electrical apparatus and particularly to the coil stacks and spacers therefor of electrical apparatus.

In assembling the coil stacks for electrical apparatus, and particularly the high voltage coil stacks for network transformers, coils are stacked in alignment with each other and maintained in spaced relation by spacers of suitable insulating material. The coils are spaced in the stack in I. order to permit an insulating fluid to pass therethrough when the coil and core assembly is im-' mersed in the insulating and cooling medium. The coil assembly with the spacers therebetween is securely clamped by suitable end plates for I maintaining the coils and spacers in assembled relation. I

In clamping or tightening the stacked coil assembly, it is found that severe abrasion of the coils is encountered adjacent the spacers between the coils. Such abrasion is more often found where there is a variation in the wire or insulation thickness or when the conductor edge is sharp or has burrs present. This abrasion or cutting of the coil insulation adjacent the hard and rigid spacers is sometimes suflicient to cause a turn-to-turn failure of the coil under test conditions with the result that the coils must be rejected. Sometimes the insulation failure does not show up until the transformer has been placed in service with the a result that the customers service is interrupted and expensive repairs are necessitated.

An object of this invention is to provide for maintaining a stack of coils in spaced relation without damaging the insulation of the coils.

' 86 Another object of this invention is to provide for so cushioning the coils of electrical apparatus when stacked in spaced relation as to prevent abrasion of the coil insulation.

A further object of this invention is to provide 40 a spacer member which will maintain the coils of an electrical apparatus in spaced relation without damaging them.

A more specific object of this invention is the provision of an electrical apparatus having stacked coils spaced by means of a spacer member which cushions the coils when assembled while maintaining them in spaced relation.

Other objects of this invention will become ap- 50 parent from the following description when taken in conjunction with the accompanying drawing, in which:

Figure 1 is a side elevational view of a core 55 this invention;

Fig. 2 is a perspective view of a portion of the coil assembly of Fig. 1;

Fig. 3 is a top plan view of a spacer member employed in the coil assembly of Fig. 2; and

Fig. 4 is a sectional view taken along the line 5 1V-IV of Fig. 3.

Referring to the drawing, and particularly to Fig. 1, this invention is illustrated with reference to a core-type transformer core and coil assembly III in which each of the coils l2 and I4 is disposed about a leg of the core I6. In order to provide for the circulation of an insulating and cooling medium. in the assembly when the core and coil assembly III is mounted in the cooling medium in a suitable enclosing casing (not 16 shown), each of coils l2 and H is constructed of a plurality of coil sections assembled in spaced relation to each other.

As illustrated in Fig. 2, the coil sections forming the coils l2 and I4 are spaced apart by a plu- 20 rality of spacer members l8 so disposed between the sections and so arranged about the coils as to provide spaces between them for permitting the free circulation of the cooling medium. between the coils. The spacer members I8 are of insulating material, as will be described more fully hereinafter, and are of elongated or rectangular shape, as shown in Fig. 3, having a length sufiicient to extend over the coil when disposed radially thereabout. In order to hold the spacers in position between the coils, each of the spacer members is provided with a notch 20 for receiving a rod 22, illustrated in Figs. 1 and 2, which extends between the outer coils across their edges and at right angles to the planes of the coils.

In order to maintain the spaced coils in assembled position, end plates 24, as shown in Fig. 1, are disposed adjacent the outer coil surfaces of the coil stack and secured together by means of a plurality of tie rods or bolts 26 disposed in spaced relation about their outer edges. As the tie rods 26 are tightened, the coil sections are firmly seated on the spacer members [8 and compressed therebetween.

Since the coils are usually wound with insulation which sometimes varies in thickness, and the wire is not always of a constant size, in order to prevent abrasion of the insulation and thus prevent a possible turn-to-turn failure of the coil, spacer members are employed which will cushion the coils while maintaining them properly spaced.

As illustrated in Figs. 3 and 4, the spacer members are of composite structure made from suitable insulating material.

In the particular embodiment illustrated in II Fig. 4, the spacer member 18 comprises a body portion 28 of hard rigid insulating material, such as fullerboard. Fullerboard is extremely hard, having a hardness rating of from to as measured on the Shore Durometer Type D, as compared to a hardness of from '70 to 75 for maple wood. In order to prevent the hardness of the fullerboard spacer from causing abrasion of the insulation of the coil sections when the stack assembly is tightened between the end plates, the outer coil contacting surfaces of the body portion 28 of insulating material are provided with a soft cushioning layer 30 for contacting the coil sections.

The layer 30 may be of any suitable soft insulation, such as cloth or paper of the blotting paper type, applied directly to the outer surfaces of the insulating body 28. For practical use, the thin cushioning layer of insulating material of the spacer member should be integral with the body portion. The integral unit may be formed by gluing or sticking the soft cushion layers to the body portion with any suitable adhesive having good electrical properties and having high oil resistance. Cellulose acetate lacquer and other lacquers embodying alkyd resins are satisfactory for obtaining an integral composite structure of this type.

In manufacturing the spacer member I8, the rigid body portion 28 is constructed having a thickness equal to the distance which it is desired to maintain the coil sections apart. The soft cushioning layers 30 are thin layers, being not over, as a general rule of an inch thick, 'it being found that a layer of this thickness may be satisfactorily compressed to permit the body portion of the spacer member to maintain the coil sections a predetermined spaced distance apart, while having the properties of cushioning the coil sections to prevent abrasion of the turn insulation.

Such a device is claimed in my divisional application Serial No. 296,591, filed September 26, 1939.

In another embodiment of this invention, the

spacer member Il may be constructed from a block of fullerboard cut to the desired configuration of the spacer member and then passed through a scraping machine to present roughened surfaces of not over inch on a hard rigid insulating body having a thickness equal to the distance which it is desired to maintain the coil sections spaced. In this embodiment, the roughened surface composed of the scraped fullerboard is found to be so fine and soft as to effectively cushion the coil sections.

With the stacked coils assembled in this manner employing the cushioning spacer members, the core and coil assembly may be readily mounted in a suitable enclosing casing which contains a suitable insulating and cooling medium. In this type of structure, it is found that the spacer members hereinbefore described effect an even distribution of stress in tightening the coil assembly, while at the same time affording such a soft surface that the insulation of the coils is not affected by abrasion. Further, where edgewound coils are employed, it is found that the edge of the wire is embedded in the surface layer of the soft material of the coil spacer, reducing the possibility of slippage of the coil or of vibration of the individual conductors.

Although this invention has been described with reference to particular embodiments thereof, it is, of course, not to be limited thereto except insofar as is necessitated by the prior art and the scope of the appended claim.

I claim as my invention:

A spacer for transformer coils comprising, a body portion of hard rigid insulating material having outer opposite surfaces of soft yielding fibrous insulating material, the hard and soft insulating material being of the same composition and formed from a single unit whereby the soft surfaces are integral with the hard body portion, the soft insulating material on the surfaces of the body portion being adapted to yield under pressure of the coils to cushion them and prevent abrasion thereof.

JAMES G. FORD. 

